1. Technical Field
The invention relates to a driving method and voltage measuring method, and particularly, relates to a driving method and feed through voltage measuring method of an electrophoretic display.
2. Description of Related Art
An electrophoretic display (EPD) has characteristics of light, thin, flexible and power-saving, and it is more suitable for promoted environmental protection issue recently, therefore, it becomes a popular display technique. Driving method of the electrophoreic display is using external electric field to change the positions of charged particles. Between charged particle and electrophoretic liquor, between charged particle and back board or between multiple charged particles presents the color contrast so as to display images and reduce thickness of displays due to without a backlight module. Moreover, the charged particle can be kept at the original position without using the external electric field, and the electrophoreic display can display the original frame so as to achieve power saving.
It usually uses TFT (Thin Film Transistor, TFT) substrate to produce AMEPD (Active-Matrix Electrophoretic Display) to raise the resolution of the electrophoretic display. A gate driver outputs scanning signals in order to multiple scanning lines of the display panel so as to turn on the pixel of each row by rows. The data lines is inputted a corresponding driving signal respectively so that drives the charged particle to change the position, in which the charged particle is driven through the electric field between the pixel electrode and the common electrode. For TFT substrate, when pixels of the display panel turns on by rows, the TFT drain voltage of each pixel (equals the voltage of the pixel electrode) is not stable. Namely, the voltage of the pixel electrode has a voltage difference from the pixel turned on to turned off. The voltage difference is due to a parasitic capacitance between the gate and the drain of the TFT, and the voltage difference is generally named feed through voltage.
In summary, for the active-matrix electrophoretic display produced by TFT substrate, it is similarity generated the parasitic capacitance between the gate and the drain of the TFT so that the pixel electrode voltage of each pixel decreases a feed through voltage when the pixel is turned off. Due to the electrophoretic display drives the charged particle through the electric field between the pixel electrode and the common electrode (the voltage difference between the pixel electrode and the common electrode), and the decrease of pixel electrode voltage affects the moving quality of the charged particle so as to affect the frame quality.
Moreover, since a liquid crystal display is similarly produced by TFT substrate, the liquid crystal display also has the problems of the feed through voltage. The liquid crystal display recovers the initial state automatically after stopping driving, so the feed through voltage of the liquid crystal display can be found through the frame flicker level. But, charged particles within the electrophoretic liquor will keep at the driving state after stopping driving so that the feed through voltage of the electrophoretic display can't be found through the frame flicker level.